1. Field of the Invention
The present invention relates to universal serial bus (USB) techniques, and in particular relates to USB 3.0 techniques.
2. Description of the Related Art
FIG. 1 shows a block diagram of a USB system. As shown, the USB system comprises a host 102, a USB device 104 and a USB cable 106. The USB cable 106 connects the USB device 104 to the host 102, and the transmission protocol is a USB 3.0 protocol.
When normally operating, both the host 102 and the USB device 104 are in a normal operation state (a U0 state). In the U0 state, the host 102 and USB device 104 receive or transmit data packages normally. Also, a user can disable the USB transmission from the host 102 side. For example, the operation system (OS) of the host 102 may provide a command, “removing the USB device”, to disable the USB transmission of the host 102.
However, for conventional techniques, when the USB transmission is disabled from the host 102 side, the USB device 104 side is not notified of the change of the operation state of the host 102. Thus, the USB device 104 continues to operate in the normal operation state (U0 state), consuming unnecessary power.